The present invention relates to a protector for use in telecommunications and, more particularly, to an improved grounding arrangement for a protector which provides a more reliable grounding.
Protectors for use in telecommunications are provided in user ends, main distributing frames, arrester frames or cable distributing boxes. It is known there are three types of protectors for use in telecommunication system, i.e., lightning arresters, fuses, and thermal coils. The lightning arresters may protect the switching networks from high-voltage damage due to abnormally high voltage and current that can result from lightning strikes. The abnormal high-voltage pulses induced by lightning strikes are introduced into the discharge device in the arrester as to ground the inlet prongs thereby protecting the switching networks from the high-voltage pulses damage. It is known that there are six prongs provided in the base portion of a protector in the telecommunication industry. They are two inlet prongs for receiving electrical signals from a transmission source, one warning prong for sending a warning signal when the protector is struck by lightning, two outlet prongs for passing electrical signals to a receiving end, and one grounding prong for grounding the high-voltage pulses when the protector is struck by lightning.
A cross-sectional view of a conventional lightning arrester 20 is shown in FIG. 5. Shown in the base portion 24 are two inlet prongs 201, 202 in solid lines and two outlet prongs 203, 204 in phantom lines being respectively arranged behind prongs 201, 202. A warning prong 206 and a grounding prong 205 are respectively provided between the inlet prongs 201 and 202 and the outlet prongs 203 and 204. Two conducting plates 21a, 21b each has a bent portion to define a higher portion and a lower portion. The conducting plates 21a, 21b have the end in the lower portion secured on the base 24 for the higher portion to clamp an arrester device 25 e.g., a carbon arrester, via a pair of tin bits 26a, 26b. An arrester holder 250 is provided for clamping the arrester device 25 and electrically coupling the ground portion of the arrester device 25. The arrester holder 250 is directly connected to the grounding prong 205. The lower portions of the conducting plates 21a, 21b are electrically coupled respectively to the outlet prongs 203, 204, via two thermistors 29a, 29 b, and are respectively clamped by two contact springs 22a, 22b, which having one end secured on the base portion 24 of the protector 20. The interconnection between the inlet prongs and the outlet prongs is thus formed. When the protector is in normal state, i.e., the protector is not struck by the lightning, the electrical signals received by the inlet prongs 201, 202 will pass to the outlet prongs 203, 204 via thermistors 29a, 29b. When high-voltage pulses due to lightning strikes are induced on one inlet prong, e.g. inlet 201, high-voltage pulses flow to the arrester device 25 via tin bit 26a, which in turn causes the arrester device 25 to discharge. The tin bit 26a will start to melt due to the heat generated by the discharge effect. Thus, the conducting plates 21a will move toward the arrester device 25 and the conducting plate 21a will contact the arrester holder 250. Thus, the high-voltage pulses induced by lightning strikes will be grounded via the grounding prong 205. A T-shape conducting plate 23 connected to an indicating lamp 27 via an electrical line 28 is placed between the other ends of the conducting plate 21a, 21b. As the conducting plate 21a moves toward the arrester device 25, the conducting plate 21a will contact the wing portion 230a of the T-shape conducting plate 23. Thus, the indicating lamp 27 will be illuminated to indicate that the protector 20 has been struck by lightning and has to be replaced. The indicating lamp 27 is further serially connected to the warning prong 205 so as to send a warning signal to other apparatus. When the inlet prong 202 is struck by lightning, the operative movement is similar to above description and is therefore not detailed here again.
Accordingly, there is only one inlet prong of a conventional protector grounded when one inlet prong is struck by lightning. While the other inlet prong is not grounded, thus the grounding of such conventional protector is not sufficient.